Method of and apparatus for lapping shoulders



April 28, 1959 E. F. KATZKE 2,883,802 METHOD OF AND APPARATUS FORLAPPING SHOULDERS Filed Sept. 24, 1956 2 Sheets-Sheet 1 fi'ncsz i wkApril 28, 1959 INVEN TOR. 5172852 F Kazfgka United States Patent METHODOF AND APPARATUS 'FOR LAPPING SHGULDERS Ernest F. Katzlre, Des Plaines,.Ill. ass'ignor to Crane Packing Company, Morton Grove, 111., acorporation of Illinois Application September 24, N56, Serial No.611,495

15 Claims. (or. 151-125 The present invention relates to lappingmachines and methods and more particularly to apparatus for lapping aflat annular shoulder on an object where .the shoulder is spaced fromthe opposite ends of the object, as well as to a method which, whencarried .out on the object undergoing lapping, will result in themaintenance of 'a properly and accurately dressed lap surface on themachlne which performs the lapping operation.

Heretofore, the automatic lapping of such shoulders, as distinguishedfrom hand lapping operations, has been carried out by means of a fiatrotating lap surface, utilizing one or the other of two more or lessbasic lapping methods. .Either the lap surface is provided with acentral axial opening which receives the protruding end of the objectundergoing lapping so that the shoulder which is to be lapped rests onthe lap surface at the rim of the opening, or the lap surface is formedwith an annular groove therein of sufficient depth to completely receivethe protruding end of the object with the shoulder to be lapped restingon the lap surface in the edge regions of the groove and straddling thelatter. The latter method is disclosed in US. Patent No. 2,597,382,issued to Raymond G. Roshong on May 20, 11952. In either case, relativerotation or movement is set up between the lap surface and article tocreate the necessary abrading effect. ,In the former instance, the sameunvaryingabradingarea .of the lap surface is presented to the shoulder,resulting in rapid grooving of the lap surface so that it isnecessary toremove and refinish the lap surface at .shortintervals. On the otherhand however, substantially all of the surface area of the shoulderundergoing lapping ispresented simultaneously to the lap surface duringthe entire .lapping cycle so that efficient lapping of the shouldertakes place. In the latter instance, a continuous presentation of a newor different a'brading area'is presented .to the shoulder and thearrangement makes possible the use of so-called conditioning or wearrings .to maintain the lap surface in its original or fiat condition inaccordance with the width of the groove required to accommodatetheprotruding portions of the articles necessitates the use .of a lapsurface of large diameter and the provisionofalap plate having such alarge diameter is costly.

It is accordingly an object of this invention to provide a method oflapping shouldered objects which combines .the advantageous features ofeach of the above outlined methods of lapping shoulders .on articleswhile, :at the same time, overcoming the limitations that are attendantthereon.

2,883,802 Patented Apr. 28,

purview a shoulder lapping method wherein, the type of lap surfaceultilized in connection with the first described method is employed foractual lapping operations upon the shoulder undergoing lapping while theconditioning or wear ring principle utilized in connection with thesecond described method is employed for conditioning the lap surface. 7

A further object of this invention is the provision of apparatus forcarrying out the foregoing methods and specifically, the provision of anannular lap surface associated with a single lap plate whichcontinuously dresses one side of an annular lap while the opposite sidethereof is lapping a shouldered article. Such condition- .ing operationtaking place and being elfected on one annular lap surface associatedwith a single lap plate simultaneously with the use o'fanother annularlap surface on the same lap plate for actual lapping operations on theshoulder undergoing lapping. By such an arrangement, a relatively smalldiameter lap plate may be employed for shoulder lapping operations whileadditionally no time is lost in the partial dismantling operations whichare attendant upon lap plate removal and refinishing operations.

These and other objects of this invention will become apparent from thefollowing detailed description when taken together with the accompanyingtwo sheets of drawings showing a preferred embodiment of the inven tionand a minor modification thereof.

In these drawings:

Fig. 1 is a fragmentary perspective view of a lapping machineconstructed in accordance with the principles .of the present inventionand, .for illustrative purposes, shown lapping of the bolting flangeassociated with the cylinder assembly of an aircraft engine.

Fig. 2 is a plan view of a reversible annular lap plate employedin-connection with the invention.

Fig. .3 is a plan view of the portion of the machine shown in Fig. 1. p

Fig. 4 is an enlarged sectional view taken substantial- .ly along thevertical plane indicated by the line 4-4 of Fig. 1, and

Fig. 5 is a fragmentary sectional view similar to Fig. 4 showing aslightly modified form of reversible lap plate operatively applied tothe aircraft cylinder bolting flange.

Referring now to the drawings for a detailed description of theinvention and in particular to .Figs. 1 .and 3,: .portion of a lappingmachine framework 10 is shown, the portion illustrated being in the formof a generally rectangular casing providing a table top 12 and dependingsides .14 within which all of the operative lap plate drivingtinstrumentalities including the motor, reduction gearing, etc. ,(notshown) are enclosed. The table top 12 As a more specific obje'ctinventionhaswit'h in its is formed with an opening 16 in which there ismounted .for rotation about .a vertical axis a lap plate 18 having anannular flat lap surface 20 defined by inner and outer peripheral edges22 .and 24, respectively. The lap plate 18 projects slightly above thelevel of the table top 12 so that the annular lap surface 20 is disposedslightly above the plane of the table top 12.

.For convenience of description the lapping region immediately above thelap plate 18 may be divided into three sectors and in one of thesesectors there is disposed a wear ring 26 which rests loosely by gravityon the lap surface 20 and overhangs both the inner and outer peripheraledges 22 and 24 thereof, respectively. The wear ring 26 is provided witha flat annular abrading surface 28 on its underneath side which has anabrading effect on the lap surface 20, and means are provided wherebythe radial position of the ring 26 may be adjusted to bring the surface.20 to the desired degree of flatness from a condition of concavity or acondition of convexitytin a manner which has been made clear in theabove menaesaeoa tinned reissue patent to Bullard. The ring 26 alsoserves to remove from the lap surface 20 any surface irregularities orscratches which may be present therein.

Still referring to Figs. 1 and 3, the means whereby the radial positionof the wear ring 26 may be varied is similar to that shown in the abovementioned patent to Roshong and comprises a so-called roller barconstruction including a yoke member 30 adjustably located relative toframe by a pin-and-slot connection 32 and clamped by a bolt assembly 34to a horizontally disposed generally arcuate face plate 36, the latterbeing held above the table top 12 by anchoring studs 38 and spacer rings40. The free ends of the yoke arms carry antifriction rollers 42 whichengage the outer cylindrical surface of wear ring 26 and restrain thering against revolution about the axis of the rotating lap surface 20while at the same time permitting the ring to rotate freely about itsown axis due to its frictional contact with the lap plate, all in amanner clearly set forth in the Roshong patent.

Referring now to Figs. 1 and 4, the lap surface 20, which hereinafterwill be referred to as the primary lap surface, is adapted to receivethereon one or more annular lap plates 44, two such plates being shownin Fig. 4, each of which is in the form of a ring having annularsecondary lap surfaces 46 formed on opposite sides thereof. Surfaces 46are designed for use in lapping the annular shoulder of an object whenthe shoulder is offset from an end of the object in such a manner thatthe protruding end requires a clearance space before the shoulder may bepositioned against the lap surface. For illustrative purposes herein theobject to be lapped by each secondary lap plate 44 is shown as being inthe form of a cylinder as sembly for aircraft engines wherein thecylinder body 50 is formed with a radially extending continuous annularbolting flange 52 providing the shoulder 53 which it is desired to lapand having a series of bolt holes 54 extending therethrough and arrangedin spaced relation therearound. The lower part 55 of cylinder 50 extendsdownwardly from the inner regions of the bolting flange 52 and precludesaccommodation of the shoulder 53 on conventional flat lap plates havingcontinuous or uninterrupted flat circular lap surfaces.

Each secondary lap plate 44 is formed with a cylindrical outer surface56 around which there extends a ring gear 57 having radially disposedteeth 58 thereon. The gear 57 may be press-fitted, shrunk, welded orotherwise secured to cylindrical surface 56 approximately midway betweenthe respective planes of the two flat secondary lapping surfaces. Thelap plate 44 is [formed with a central axial opening 60 therethroughdefining a cylindrical bore or wall 62 the diameter of which is slightlylarger than the external diameter of the lower part 55 on the cylinderbody 50 so that when the plate 44 is resting on the upwardly facing lapsurface 20 of the primary lap plate, with either secondary lap surface46 in lapping engagement with the surface 20, the part 55 may be received in the bore 62 which provides a clearance for it so that theannular shoulder 53 on the bolting flange 52 may seat on the other orupwardly presented secondary lap surface and make intimate lappingcontact in the immediate vicinity of the inner peripheral regionthereof.

As best seen in Fig. 3, the central region of the primary lap plate 20is formed with a shallow circular well 64 which defines the innerperiphery 22 of the lap surface 20. The drive shaft 66 for lap plate 18projects upwardly through said plate and well above the level of the lapsurface 20 and has affixed thereto a central hub gear 63 hav ing aseries of radial teeth 70 thereon designed for meshing engagement withthe teeth 58 provided on the ring gears 57 associated with the secondarylap plates 44. The mean height of the hub gear 68 above the plane of theprimary lap surface 20 is substantially equal to the mean height of thering gear 57 of each lap plate 44 regardless of which lap surface 46thereof is resting upon the primary lap surface 20. The secondary lapplates'44 t are symmetrical with respect to a plane extendingtransversely and centrally through the same and they are thereforereversible on the primary lap surface so that whichever lap surface ispresented upwardly, that surface is positioned for lapping operations onthe cylinder shoulder 53 while the opposite lap surface is presenteddownwardly and in contact with the primary lap surface so that it may heabraded by the latter and brought to a condition of flatness, all in amanner and for a purpose that will be made clear presently.

The various secondary lap plates 44, when operatively resting on therotating primary lap surface 20, are held against revolution about theaxis of the latter surface, as well as being held in such positions thattheir respective ring gears 57 mesh with the central hub gear 68, bymeans of roller bar assemblies similar to that already described inconnection with the wear ring 26 and similarly designated in thedrawings. It is to be noted that the overall height of the variousroller bar assemblies including the yokes 30 and rollers 42 is less thanthe mean height of the ring gears 57 above the primary lap surface 20 sothat there will be no interference with the operation of the rollers 42which bear against the outside cylindrical surface 56 of the secondarylap plates 44 when the machine is in operation.

As shown in Figs. 1 and 3, the entire weight of the cylinder assemblies50 is supported on the secondary lap plates 44 at the regions where theshoulders 53 of the bolting flanges 52 engage the inner peripheralregions of the plates. In order to create relative movement for lappingpurposes between each assembly 50 and the sec-- ondary lap plate 44 onwhich it rests, a rod 72 has one end thereof pivotally secured to astandard 74 mounted on the upper face of the plate 36, the said one endof rod '72 being vertically slidable on and rotatable about a stud 75which projects upwardly from the standard. The elevation of the rod 72above plate 36 is determined by a series of spacer collars 76telescopically received over stud 75. A compression spring 78 encirclesthe stud and bears downwardly at one end on the rod, the other endreacting against a tension-adjusting nut 80 threadedly received on theupper end of the stud. The free end of the rod 72 carries a pin 82, thelower end of which is adapted to extend into one of the bolt holes 54provided in the bolting flange 52 so that the rod extends approximatelytangential ly of the bolting flange 52 and supplies the countertorque orreaction force necessary to hold the bolting flange 52 against rotationwith the secondary lap plate 44 on which it is supported.

As shown in Fig. 1, the machine is provided with a storage and agitatortank assembly for the grit and the vehicle in which it is suspended thegrit and vehicle comprising the abrading compound for the lappingoperation. This abrading compound is fed through an aperture under thecontrol of a solenoid-actuated valve mechanism designated in itsentirety at 92 and travels by gravity along a thin rod or wire 94, thefree end of which may make contact with a surface of the wear ring 26 todeposit the compound thereon whence it flows onto the lap surface 20 andbecome distributed thereover in the manner set forth in theabovementioned patent to Bullard.

In the operation of the machine and according to the method of thepresent invention, with the various machine parts in the position inwhich they are shown in Fig. l, and with the cylinder assemblies 50 inposition on the secondary lap surfaces 46, rotation of the primary lapplate 18 and its drive gear 68 in a counter-clockwise direction asindicated by the arrow will cause the secondary lap plates 44 to bepositively driven in a clockwise diree tion as likewise indicated byarrows. The wear ring 26, however, which receives its motivating torqueby induced rotation picked up from frictional contact with the primarylap surface20, will rotate in a counter-clockwise direction and thusperform its intended lap dressing function as previously described.

Since the cylinder assemblies 50 are held stationary,

the counter-clockwise rotation of their respective secondary lap plateswill supply the necessary relative rotation between the two parts, andlapping of the shoulder 53 of the bolting flange 52 of each assemblywill take place. It is obvious that continued and protracted lapping ofthe shoulder 53 of each cylinder assembly 50 will have an abradingeffect on the primary lap surface 46 tending to cut or wear an annulargroove on that portion of the surface which is in contact with theshoulder. Thus, according to the present method, during any givenlapping cycle as defined above, it is necessary that the lap plate 44 bereversed by turning the same upside down on the primary lap surface 20and causing the underneath side of the plate, which has been freshlyconditioned by virtue of its contact with the surface 20, to be directedupwardly and presented to the shoulder 53. Such reversal of eachSecondary lap plate 44 may be resorted to several times during eachlapping cycle, that is, during the lapping of a single shoulder, thefrequency of reversal depending, of course, upon the character andhardness of the surface undergoing lapping as well as upon the characterof the lapping compound employed on the secondary lap surface 46.

The lapping compound used upon the secondary lap surfaces 46 is spreadevenly over the upper surface of each lap plate 44 utilizing either abrush or a spatula for the purpose. A paste type of compound ispreferred and, each time a reversal of the lap plate is made asdescribed above, a fresh application of the abrasive compound isresorted to.

Reversal of secondary lap plates 44 is accomplished preferably byshutting down the machine to stop all rotation of the primary andsecondary laps, and then removing cylinders 50 after raising rods 72against the action of springs and then rotating the raised rods clear ofthe plates 44. Said plates 44 may then be raised from lap surface 20,turned over, and then replaced on surface 20 with the teeth of gear 57meshing with the teeth of gear 68. Cylinders 50 are then replaced onplates 44, pins 82 'of rods 72 are placed in the bolt holes 54 and themachine is restarted.

It is to be noted from an inspection of Fig. 3 that the character of theteeth 70 on the hub gear 68 and the teeth 58 on the ring gears 57 issuch that these gears are capable of various degrees of mesh. By such anarrangement, limited radial shifting of the secondary lap plates 44 ismade possible utilizing the roller bar yokes 30 to effect theadjustment.

The annular configuration of secondary laps 44 may result, in the eventof the need of a large opening 62 therein for the reception of acorrespondingly large diameter protruding portion of a shoulderedarticle, in the secondary laps approximating in size and shape the wearring 26, and hence the secondary laps 44 may, under such circumstances,serve to condition primary lap surface'20 as to contour even while lapsurface 20 is removing the groove formed in the secondary lap surface bythe shouldered article. In such event, the wear ring 26 may be dispensedwith and the capacity of primary lap 18 may be increased by substitutingfor wear ring 26 an additional secondary lap 44.

In accordance with conventional practice, the various lap surfaces 20and 46 may be radially grooved as indicated at 100 tofac'ilitatedistribution and drainage of the 'ab'rading compound as well as toimprove the lapping characteristics of the lap plates.

In Fig. 5 is shown a slightly modified form of secondary lap plate 144which is capable of use in connection with "the primary lap plate 18 andin substantially the same manner in which the lap plate 44 is used.Because of the similarities between the lap plates 44 and 144,corresponding parts have been given similar reference numerals but of ahigher order. Thus the ring gear is given the numeral 157, the centralopening in lap plate 144 is numbered 160 and the wall defining theopening 160 is.

numbered 162. It' i's'understood'that the-a plication, use and removalof secondary lap plates 144- from primary lap plate 18 are identicalwith those relating to lap plates 44. In lap plate 144- the peripheralregions have been relieved on both sides as indicated at 101. The

7 overall weight of the lap-plate 144 is lessened by this expedient and,additionally, during the lapping cycle the primary lap plate 18 isrelieved of the burden of removing much excess material on the secondarylap plate which is not subject toany abrading action by the shoulder 53and which, as a consequence, is itself not worn.

It has been found that shoulders such as the shoulder 53 having boltholes or other voids formed therein have a tendency for excess lappingto take place in the annular regions of both laps occupied by the boltholes or other voids, and it is believed that such a condition is theresult of abrasive particles building up within the bolt holesthemselves and exerting an undue abrading effect on the rimportions ofthese holes while comparatively starving the remaining portions of thelap surfaces. Another and perhaps additional cause for such excessivewear may, it is believed, be caused by oversize particles of abrasivemaking minute chips on the edge of the bolt hole rims as they slideunder the shoulder initially and before they are reduced in size bytheir abrasive action. In any event, it has been found that by drillinga series of holes through the lap plate as indicated at 103, with theholes preferably being the same in number and diameter as the number anddiameter of the bolt holes formed in the shoulder undergoing lapping,the excessive accumulation of abrasive is drained from the surface ofthe lap plate and the condition is remedied. The holes 103 are, ofcourse, effective in this manner when the lap plate 144 is reversed.

The invention is not to be limited to the exact arrangement of partsshown in the accompanying drawings or described in this specification asvarious changes in the details of construction may be resorted towithout departing from the spirit of the invention. Only insofar as theinvention has particularly been pointed out in the accompanying claimsis the same to be limited.

I claim:

1. The method of lapping a surface on an article while simultaneouslydressing a lap surface which comprises forming a lap plate withoppositely directed lap surfaces, effecting rotation of the lap plateabout an axis passing through both surfaces, applying the article to oneof said rotating lap surfaces and creating relative motion between thearticle and surface to perform lapping operations on the article whilesimultaneously applying a dressing tool to the other rotating lapsurface and creating relative motion between the tool and latter surfaceto dress the latter surface, and thereafter inverting the lap platerelative to the article and dressing tool and rotating the inverted lapplate relative to the article and tool so that the article is applied tothe previously dressed lap surface and the dressing tool is applied tothe lap surface which, by virtue of its previous contact with thearticle has itself become abraded.

2. The method of lapping a surface on an article while simultaneouslydressing a lap surface which cornprises forming a lap plate withoppositely directed lap surfaces, effecting rotation of the lap plateabout an axis passing through both surfaces, simultaneously applying thearticle to one side of the lap plate and a dressing tool to the otherside thereof and utilizing the rotation of the lap 'plate to establishrelative motion between the same and the article and dressing toolrespectively, and repeatedly inverting and rotating the lap plate sothat the article and dressing tool are alternately and successivelyapplied to the opposite sides of the lap plate.

3. The method of lapping a surface on an article while simultaneouslydressing a lap surface which comprises forming a lap plate withoppositely directed lap surfaces, effecting rotation of the lap plateabout an axis passing through both surfaces, applying the article to oneof said rotating lap surfaces and creating relative motion between thearticle and surface to perform lapping operations on the article whilesimultaneously applying a dressing lap to the other rotating lap platesurface and creating relative motion between the dressing lap and lattersurface to dress the said latter surface, continuously dressing the saiddressing lap, and periodically inverting the lap plate relative to thearticle and dressing lap and rotating the inverted lap plate relative tothe article and dressing lap so that the article is applied to thepreviously dressed lap plate surface and the dressing lap is applied tothe lap plate surface which, by virtue of its previous contact with thearticle has itself become abraded.

4. The method of lapping an annular shoulder on an article whilesimultaneously dressing a lap surface which comprises forming a lapplate with oppositely directed lap surfaces and an opening inwardly ofeach said lap surface into which the portion of the article below theshoulder may extend, mounting the article on said plate with theshoulder contacting one of the lap surfaces, effecting rotation of thelap plate about an axis passing through both surfaces while restrainingthe article against rotation with the plate to effect an abrading actionbetween the article and plate, simultaneously abrading the opposite sideof the plate with a rotating lap having an annular lap surface thecenter of rotation of which is eccentric with respect to the axis ofrotation of the plate to expose a portion of the annular lap surface,and continuously dressing the annular lap by a dressing ring disposedupon the exposed portion of the annular lap surface.

5. In an apparatus for forming a true surface of predetermined contourupon an article, in combination, a primary lap plate mounted forrotation about a vertical axis and having a horizontal primary lapsurface, means for rotating said lap plate, a secondary lap plate havingtwo oppositely directed parallel secondary lap surfaces, one on eachside thereof, said secondary lap plate being adapted to be looselyreceived on the primary lap surface with either secondary lap surface incontact therewith, means operable when said secondary lap plate isreceived on said primary lap plate in either position thereof forrestraining said latter lap plate against revolution about the axis ofthe primary lap plate, said secondary lap plate when in position on saidprimary lap plate in either position thereof being adapted to looselyreceive thereon the article to be lapped with the article resting uponthe then uppermost secondary lap surface, and means for establishingrelative movement between the article and the secondary lap platewhereby relative lapping motion is created between the article andsecondary lap plate.

6. In an apparatus for forming a true surface of predetermined contourupon an article, the combination set forth in claim including,additionally, means operable when said secondary lap plate is inposition on said primary lap plate in either position thereof forpositively rotating the same in a direction opposite to the direction ofrotation of said primary lap plate.

7. In an apparatus for forming a true surface of predetermined contourupon an article, the combination set forth in claim 5 including,additionally, means operable when said secondary lap plate is inposition on said primary lap plate in either position thereof forpositively rotating the same in the same direction as viewed from afixed point.

8. In an apparatus for forming a true surface of predetermined contourupon an article, the combination set forth in claim 5 includingadditionally, means on the primary lap for conditioning the primary lapwhile said primary lap is operating upon the secondary lap restingthereon.

9. In an apparatus for forming a true surface of predetermined contourupon an article, the combination set forth in claim 8 wherein saidrotating means comprises a central hub gear on said primary lap plate inaxial alignment therewith, and a ring gear on said secondary lap platein constant mesh with said hub gear, said hub and ring gears beingformed with elongated teeth capable of varying degrees of radial meshingengagement with each other, said restraining means including means forradially shifting the position of the secondary lap plate relative tothe primary lap surface.

10. In an apparatus for forming a true surface of predeteterminedcontour upon an article, the combination set forth in claim 9 whereinsaid restraining means comprises antifriction elements positioned toengage the outer surface of said secondary lap plate in either positionthereof at spaced points therearound and subtend an arcuate increment ofthe plate therebetween so that the vectorial forces exerted upon thering during rotation of the primary lap plate tending to move thesecondary lap plate outwardly and radially away from said hub gear aredirected against said antifriction elements.

11. In an apparatus for forming a true surface of predetermined contourupon an article, in combination, a primary lap plate mounted forrotation about a vertical axis and having a horizontal primary lapsurface, means for rotating said lap plate, a secondary lap plate havingtwo oppositely directed parallel secondary lap surfaces, one on eachside thereof, said primary lap plate beingadapted to loosely receivethereon the secondary lap plate with either secondary lap surface incontact therewith, a hub gear mounted on said primary lap plate in axialalignment therewith and slightly above the level of said primary lapsurface, a ring gear mounted on said secondary lap plate and encirclingthe latter in the medial region thereof, the distance between said ringgear and either secondary lap surface being equal to the distancebetween said hub gear and the primary lap surface whereby said ring gearis engageable with the hub gear in either position of the secondary lapplate, a support positioned adjacent the edge of said primary lap plateand above the level of said primary lap surface, and means mounted onsaid support and operable when said secondary lap plate is positioned onsaid primary lap surface in either position thereof for restraining thesecondary lap plate against revolution about the axis of said primarylap sure face and for holding the secondary lap plate in a positionwherein the ring gear thereon meshes with said hub gear.

12. In an apparatus for lapping a shoulder on an article ondary lapsurfaces, one on each side of the ring and surrounding the openingtherein, said secondary lap plate being adapted to be loosely receivedon the primary lap surface with either secondary lap surface in contacttherewith, the opening in said secondary lap plate being adapted toreceive therein the protruding end of the article in either position ofthe plate with the shoulder thereof resting upon the adjacent secondarylap surface in lapping relationship, means operable when said secondarylap plate is received on said primary lap plate in either position forrestraining said latter lap plate against revolution about the axis ofthe primary lap plate, and means for establishing relative movementbetween the article, when received on the secondary lap plate, and thelatter lap plate whereby relative motion is created between the articleand secondary lap plate.

13. In an apparatus for lapping the sealing surface or shoulder of abolting flange having a series of spaced bolt-receiving openingstherethrough and wherein the bolting flange extends radially from themedial regions of an article so that a portion of the article protrudesforwardly from the bolting flange, in combination, a primary lap platemounted for rotation about a vertical axis and having a horizontalprimary lap surface, means for rotating said lap plate, a secondary lapplate in the form of a flat ring having a central opening therein andtwo oppositely directed parallel annular secondary lap surfaces, one oneach side of the plate and surrounding the opening therein, saidsecondary lap plate being adapted to be loosely received on the primarylap surface with either secondary lap surface in contact therewith, theopening in said secondary lap plate being adapted to receive therein theprotruding portion of the article in either position of the plate withthe sealing surface of the bolting flange resting upon the adjacentsecondary lap surface in lap-ping relationship, said secondary lap platebeing formed with a circular series of holes therein in radial registerwith the bolt-receiving openings on said bolting flange when the objectis positioned on the secondary lap plate in either position of thelatter, said holes constituting drainage channels for the abrasivecompound on said secondary lap surfaces, means operable when saidsecondary lap plate is received on said primary lap plate in eitherposition for restraining said latter plate against revolution about theaxis of the primary lap plate, and means for restraining the article,when received on the secondary lap plate, against bodily movement withsaid latter lap plate whereby relative movement is created between thearticle and secondary lap plate.

14. In an apparatus for lapping the sealing surface or shoulder of abolting flange having a series of spaced boltreceiving openingstherethrough and wherein the bolting flange extends radially from themedial regions of an article so that a portion of the article protrudesforwardly from the bolting flange, the combination set forth in claim 13wherein said latter restraining means comprises a stationary supportpositioned adjacent said primary lap plate, a thrust rod pivoted to saidstationary support, and an anchoring pin carried at the free end of saidthrust rod and receivable in a selected opening in said bolting flangeof the article when the latter is in position on said secondary lapplate.

15. In an apparatus for lapping the sealing surface or shoulder of abolting flange having a series of spaced bolt-receiving openingstherethrough and wherein the bolting flange extends radially from themedial regions of an article so that a portion of the article protrudesforwardly from the bolting flange, the combination set forth in claim 13wherein the number and diameter of said holes in the secondary lap plateand the spacing thereof, are equal to the number, diameter and spacingrespectively of the bolt-receiving openings in said bolting flange onthe article.

References Cited in the file of this patent UNITED STATES PATENTS2,597,382 Roshong May 20, 1952

